Method and apparatus for automated composite-based manufacturing

ABSTRACT

An apparatus and method for the automated manufacturing of three-dimensional (3D) composite-based objects is disclosed. The apparatus comprises a material feeder, a printer, a powder system, a transfer system, and optionally a fuser. The method comprises inserting a stack of substrate sheets into a material feeder, transferring a sheet of the stack from the material feeder to a printer, depositing fluid on the single sheet while the sheet rests on a printer platen, transferring the sheet from the printer to a powder system, depositing powder onto the single sheet such that the powder adheres to the areas of the sheet onto which the printer has deposited fluid, removing any powder that did not adhere to the sheet, optionally melting the powder on the substrate, and repeating the steps for as many additional sheets as required for making a specified 3D object.

This application is a divisional of application Ser. No. 15/611,320filed Jun. 1, 2017 which claimed the benefit of InternationalApplication PCT/US17/17672, filed Feb. 13, 2017, which claimed thebenefit of U.S. Provisional Application No. 62/294,997, filed Feb. 12,2016. Applications 15/611,320, PCT/US17/17672 and 62/294,997 are herebyincorporated by reference in their entireties.

FIELD OF THE TECHNOLOGY

The present invention relates to additive manufacturing and, inparticular to an apparatus for automated manufacturing ofthree-dimensional composite-based objects.

BACKGROUND

Additive manufacturing, such as three-dimensional printing, can be seenas largely a materials problem. One of the limitations of currentmethods is a limited materials palette and slow build speeds.

These and other limitations of the prior art are avoided by amethodology known as Composite-Based Additive Manufacturing (CBAM). CBAMis described in full in co-pending U.S. patent application Ser. No.13/582,939, filed Nov. 2, 2012, Ser. No. 14/835,690, filed Aug. 25,2015, and Ser. No. 14/835,635, filed Aug. 25, 2015, each of which areincorporated fully herein by reference.

SUMMARY

This application describes a particular method and apparatus forautomating Composite-Based Additive Manufacturing (CBAM).

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, advantages and novel features of the invention willbecome more apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawingswherein:

FIG. 1 is a schematic of an example embodiment of an apparatus forcomposite-based additive manufacturing, according to one aspect of theinvention.

FIG. 2 is an example substrate layer useable in the present invention.

FIG. 3 depicts aspects of an example embodiment of a Coanda gripperelement of an example transfer system according to one aspect of theinvention.

FIG. 4 is a different view of the aspects of the Coanda gripper elementdepicted in FIG. 3.

FIG. 5 is another view of the aspects of the Coanda gripper elementdepicted in FIG. 3.

FIG. 6 is another view of the aspects of the Coanda gripper elementdepicted in FIG. 3.

FIG. 7 depicts an example embodiment of a needle gripper element of anexample transfer system according to one aspect of the invention.

FIG. 8 depicts aspects of an example embodiment of a felted gripperelement of a transfer system.

FIG. 9 is another view of the aspects of a felted gripper elementdepicted in FIG. 8.

FIG. 10 is another view of the aspects of a felted gripper elementdepicted in FIG. 8.

FIG. 11 depicts an example embodiment of a material feeder according to

FIG. 12 shows another view of an example embodiment of a material feederaccording to one aspect of the invention.

FIG. 13 is a top-side view of an example implementation of aspects of apowder system according to one aspect of the invention.

FIG. 14 is a front-side view of an example implementation of aspects ofa powder system according to one aspect of the invention.

FIG. 15 is another top-side view of an example implementation of aspectsof a powder system according to one aspect of the invention.

FIG. 16 is a rear-side view of an example implementation of aspects of apowder system according to one aspect of the invention.

FIG. 17 is another side view of an example implementation of aspects ofa powder system according to one aspect of the invention.

FIG. 18 is a schematic diagram of an alternative example implementationof aspects of a powder system according to one aspect of the invention.

FIG. 19 depicts an example implementation of the alternative powdersystem of FIG. 18.

FIG. 20 is another view of the example implementation of the alternativepowder system shown in FIG. 19.

FIG. 21 is another view of the example implementation of the alternativepowder system shown in FIG. 19.

FIG. 22 depicts an example valve part of the alternative powder systemof FIG. 18.

FIG. 23 depicts an alternative design of the valve part of thealternative powder system of FIG. 18.

FIG. 24 depicts a roll-based continuous feed implementation.

FIG. 25 depicts a roll-based roll to sheet implementation

The above Figures show all or part of illustrative embodiments of thisinvention. The Figures do not show all of the possible details of theinvention.

DETAILED DESCRIPTION

The CBAM process described in the incorporated prior applications (U.S.patent application Ser. Nos. 13/582,939, 14/835,690, and 14/835,635) isautomated by performing the steps through a number of components orsubsystems that operate in a coordinated manner. The main components ofan example embodiment are shown in FIG. 1, and include a material feeder102, a printer 104, a powder system 106 comprising a powder applicator108 and powder remover 110, an optional fuser 112, a transfer system,and other elements that serve to connect and control the variouscomponents. While example components are shown in FIG. 1, variousalternative and optional components described below are also suitablefor use with the invention and are therefore to be considered as beingwithin the scope of the invention.

General Device Operation. The material feeder 102 holds a stack ofsubstrate sheets, such as the example carbon fiber sheets (202 a, 202 b)shown in FIG. 2, and moves them into proper position so that a singlesheet at a time can be transferred to the printer 104. Sheets aretransferred to, and positioned for, the printer 104 by means of thetransfer system. The printer 104 then deposits fluid onto a substratesheet as in the incorporated prior applications (U.S. patent applicationSer. Nos. 13/582,939, 14/835,690, and 14/835,635), and may optionallyinclude a punching mechanism for placing holes in the sheet at desiredlocations. For example the printer prints a layer of a 3D model of whicha stack of the successive layers are used use to produce a 3D object asdescribed in the above-mentioned applications. The powder applicator 108then deposits thermoplastic powder onto the substrate sheet, whereuponthe powder adheres to the areas of the sheet that have been made wet bythe printer 104. The powder remover removes powder that did not adhereto the sheet. The fuser 112, which is optional, heats the powder on thesubstrate sheet in a manner sufficient to cause the powder to melt andthereby affix to the sheet, so that the powder remains on the sheet whenand if the underlying fluid from the printer 104 dries. This cycle isrepeated for as many additional substrate sheets 202 as required formaking a specified three-dimensional (3D) part, with each sheet 202normally representing a layer of the 3D part. A roll/web based systemfor material feeding can be used in an alternative embodiment.

Transfer System.

The sheets are transferred from the material feeder 102 to the printer104, and from the printer 104 to the powder applicator, by a transfersystem. One of the problems with feeding the sheets used in the CBAMprocess is that, in the case of non-woven carbon fiber sheets and othernon-woven substrate sheets, the sheets are porous, and so conventionalmeans for picking up the sheets do not work. For example, mostlithography presses uses vacuum grippers to pick up single sheets ofpaper, but this only works because/when the paper sheets are non-porous,and so that the vacuum holds tightly against the top sheet in a stackbut not the sheets below the top sheet.

A conventional approach to solving this problem is to feed single sheetsusing rollers, such as are used in laser printers and photocopiers. Theproblem with this approach is that sheets of non-woven materials,especially non-woven carbon fiber, and other non-wovens such asfiberglass, tend to stick together, so attempting to pick up or slideone sheet from a stack of sheets causes multiple sheets to be picked upor slide. This is due in part to the fact that fibers at the edges ofeach sheet are slightly frayed, causing them to tangle with the frayededge fibers or other surfaces of the sheets directly above or below thetarget sheet. Also, stray fibers occur elsewhere thereby entangling withthe sheet above or below. For example, in the case of carbon fibersheets, the sheets are not only porous, but are also a matrix of fibersheld together with a binder and having holes or areas where there is nofiber. In these areas, the fiber from the sheet below can becomeentangled with the sheet above, causing them to stick together.

Different approaches are therefore needed for porous non-woven substratesheets, and the novel methods and devices disclosed herein are to beconsidered within the scope of the present invention. These approachesmay include the use of Coanda grippers, such as, but not limited to,those supplied by Schmalz Inc. (for example the series SCG-1 compositegrippers, and particularly Model No. SCG ixE 100 A MA), and/or needlegrippers, such as, but not limited to, those supplied by Schmalz Inc.(for example the series SNG-V needle grippers and particularly Model No.SNG-V 10 1.2 V7). These approaches may also include the use of a grippercomprising certain kinds of felt, and particularly needle-felted,non-woven filamentous or fiber material (hereinafter “felted material”),such as, but not limited to, that used as the eraser material in modelnumber 81505 “Expo White Board Care” block eraser made by NewellRubbermaid Office Products.

As shown in FIGS. 1 and 3-7, a preferred embodiment of the grippersubsystem comprises a framework of rails 114 and belt drivers definingtwo XY positioners 116 further including stepper motors to additionallyprovide movement in the Z direction as further described below(collectively an “XYZ Positioner”). The system can be devised so thatfor each positioner, only X movement or XZ movement is required in whichcase an X or XZ positioner rather than an XY or XYZ positioner could beused. In this embodiment, a Coanda gripper 118 (FIG. 3) is mounted onthe first XYZ positioner 116 and a needle gripper 120 (FIG. 7) ismounted on the second XYZ positioner 116. A Y positioner 128 is alsoshown in FIG. 1. The printer 104 is mounted on the Y positioner 128. TheCoanda gripper 118 is also depicted in FIGS. 4-6. The Coanda gripper 118is used for transferring substrate sheets 202 from the material feeder102 to the printer 104. The needle gripper 120 is used for transferringsubstrate sheets 202 from the printer 104 to the powder applicator 108.Belt drivers contribute to moving the positioners in the XY-directionand stepper motors connected to lead screws move the grippers in theZ-direction (in some implementations, while in other implementationspneumatic cylinders or solenoids in addition to stepper motors move thegrippers in the Z-direction). Both grippers are activated with forcedair, through air hoses 122 connected at one end to each gripper and atthe other end to a manifold (not shown), with air valves for startingand stopping the flow of air to the grippers. The manifold is connectedto the controller, which sends signals at the appropriate time to openand close the air valves. Both the belt drivers and the stepper motorsare in also in communication with the controller, which sends signals tothe drivers and motors to turn them on and off, thereby causing the XYZpositioners 116 to move in the X-direction, the Y-direction, and/or upor down (the Z-direction), at the appropriate times and for theappropriate distances. The Z positioning can be done by solenoids orpneumatic positioners.

Serial or Parallel Operation. The system can operate so that substratesheets 202 travel through the entirety of the subsystems only one at atime. In this embodiment, the next substrate sheet on the materialfeeder 102 does not advance from the feeder 102 to the printer 104 untilthe prior substrate sheet completes its journey through the finalcomponent in the system. Alternatively, the system can operate so thatonce a given substrate sheet is transferred from a given component, anext substrate sheet can be advanced to that component or another priorcomponent in the system. In such an embodiment, for example, as a givensubstrate sheet is being transferred by the needle gripper 120 away fromthe printer 104 (that is, to the powder applicator 108), a nextsubstrate sheet 202 a . . . n) can be transferred by the Coanda gripper118 to the printer 104 (that is, from the material feeder 102), and soon.

Felted Material Gripper Embodiment.

In an alternative embodiment, a gripper comprising felted material isused in lieu of the Coanda gripper. In this embodiment, hereinafter“felted gripper,” forced air need not be used as part of either thegripper or to blow air between or across surfaces of the substratesheets 202, though it may be used if desired. As shown in FIGS. 8-10,the felted gripper 124 comprises a plate 300 on which felted material304 is mounted. The exposed surface of the felted material 304 isdisposed so that it faces downward and is generally parallel to the topsurface of a top substrate sheet when sitting on the platform 132 of thematerial feeder 102. To pick up a substrate sheet 202 a . . . n from theplatform 132, hold-down prongs 142 are used to hold down the secondsheet. The XYZ positioner 116 lowers the felted gripper 124 until thefelted material 304 comes into contact with the top surface of the topsheet. The felted material 304 entangles with the substrate sheetmaterial and thusly grips the substrate sheet (such as topmost substratesheet 202 a). The XYZ positioner 116 retracts and picks up the sheet,the sheet is die cut with notches which are alternated as shown in FIG.2 and using the prongs the top sheet is stripped from the sheet below.In some instances the sheets are stacked on top of compliant foammaterial on the material feeder 102 to improve the compliance of thestack to improve the adherence of the felt to the sheet. The XYZpositioner 116 then moves the felted gripper 124 to the printer platen140 and the substrate sheet is placed onto the platen 140. Because thefelted gripper 124 is typically a needle felted or similar material,where the fibers of the felt are entangled and frizzy, they entangle inthe matrix of the non-woven substrate, thus allowing it to be picked upby the gripper 124.

The felted gripper 124 further comprises one or more spring-loaded pins306 with magnetic tips 308 at one end and a bearing surface 310 at theother end. The spring-loaded pins 306 are disposed so that, in theirrest position, the bottom surfaces of the magnetic pins are about evenwith the bottom surface of the felted material 304, or the bottomsurfaces of the magnetic pins may be above the bottom surface of thefelted material 304. Thus, when the felted gripper 124 comes intocontact with the top surface of a substrate sheet on the material feeder102, the pins 306 will not defeat the ability of the felted material 304of the felted gripper 124 to engage and hold a substrate sheet 202 a . .. n. The spring is disposed between upper surfaces of the plate 300 andthe bearing surface 310 of the pin 306.

In one embodiment, the surface of the platen 140 comprises ferromagneticmaterial. The entire platen 140 may be made of a ferromagnetic material,or only the surface of the platen 140, or only certain portions of thesurface of the platen 140 may comprise a ferromagnetic material. Forexample, the platen 140 may be aluminum with a thin sheet of steeldisposed on its top surface. To place a substrate sheet onto the platen140, the XYZ positioner 116 lowers the felted gripper 124 to the surfaceof the platen 140. As the bottom surface of the gripper nears the topsurface of the platen 140, the magnetic tips 308 of the spring-loadedpins 306 are attracted to and engage the ferromagnetic materialcomprising the surface of the platen 140. At this point, the substratesheet is captured between the tips of the spring-loaded pins 306 and theplaten 140. The XYZ positioner 116 then lifts the felted gripper 124away from the platen 140. Due to the magnetic forces, the spring-loadedpins 306 remain engaged with the platen 140 as the felted gripper 124begins to move away from the platen 140. As the gripper continues tomove away, the substrate sheet remains pinned to the platen 140 due tothe magnetic forces, at least until the sheet detaches from the feltedmaterial 304 of the gripper 124. Then, as the gripper 124 furthercontinues to move away from the platen 140, the springs becomescompressed so that the forces of the springs eventually overcome themagnetic forces causing the tips of the spring-loaded pins 306 todisengage from the platen 140, thereby leaving the substrate sheet 202 a. . . n on the surface of the platen 140. The length of thespring-loaded pins 306, the strength of the springs used therein, andthe strength of the magnets comprising the tips 308 of the spring-loadedpins 306 are selected so that the magnetic forces are stronger than thebond between the felted gripper 124 and the substrate sheet 202 a . . .n, and the spring forces of the pins 306 as they compress becomestronger than the magnetic forces between the tips 308 of the pins 306and the platen 140.

In an alternative embodiment of the felted gripper 124, pins withoutsprings can be used. In this embodiment, the pin is light enough orotherwise disposed so that when the felted material 304 grips asubstrate sheet 202 a . . . n on the material feeder 102, the pins willnot defeat the bond between the gripper 124 and the sheet 202 a . . . n.When the gripper 124 is moved to the platen 140, it will operate asotherwise described above. However, instead of relying on spring forcesto cause the magnetic tips 308 of the pins to disengage from the platen140, as the gripper 124 moves away from the platen 140, the bearingsurfaces 310 of the pins 306 are constrained by the plate 300 and thuslybreak the magnetic bond between the pins 306 and the platen 140.

In any of the embodiments of the felted gripper 124, a material otherthan felted material suitable to engage a substrate sheet throughentanglement or other technique may be used. Such alternative materialmay comprise, for example, but is not limited to, tape or otheradhesive, or electrostatic forces. In the case where electrostaticforces are used, the use of pins—spring-loaded or otherwise—may beeliminated. Instead, an electrical current to the gripper for generatingthe electrostatic forces may be turned on for purposes of gripping asubstrate sheet and turned off for purposes of releasing the substratesheet.

Additionally, where pins 306 with magnetic tips 308 are used, suchmagnets may be electromagnets. In this embodiment, an electrical currentto the gripper 124 for generating a magnetic field may be turned on forpurposes of causing the pins—spring-loaded or otherwise—to engage thesurface of the platen 140 and turned off for purposes of disengaging thepins 306 from the surface of the platen 140.

In a further alternative embodiment, rather than magnetic tips, the tipsof the pins—spring-loaded or otherwise—may comprise vacuum grippers. Inthis embodiment, the platen need not comprise a ferromagnetic surface.When the gripper lowers a substrate sheet 202 a . . . n onto the platen140, the vacuum grippers are turned on and thusly engage the surface ofthe platen 140, thereby clamping the substrate sheet 202 a . . . n tothe platen 140. As the gripper 124 moves away from the platen 140, thevacuum forces are sufficient to remain engaged with the platen 140surface until the substrate sheet 202 a . . . n disengages from thefelted material 304. Where spring-loaded pins 306 are used, as thegripper 124 continues to move away from the platen 140, the springforces overcome the vacuum forces to disengage the vacuum grippers fromthe surface of the platen 140. Where springs are not used, the bearingsurfaces 310 of the pins as they are constrained by the plate 300 canovercome the vacuum forces. Alternatively, instead of relying on springsor constraining of the pins, the vacuum gripper could simply be turnedoff so that the pins disengage from the surface of the platen 140 at theappropriate time.

Material Feeder.

In some embodiments, the material feeder 102 has severalsubparts/systems, including the frame and platform, sheet openings, andhold-down prongs and gripper. Alternative embodiments include a slipsheet embodiment as well as a roll/web based system.

Frame and Platform. In one embodiment, shown in FIG. 1 and in detail inFIGS. 11 and 12, the material feeder 102 comprises a frame 130, whichhouses a platform 132. The platform 132 is capable of holding a stack ofsubstrate sheets 202, which are placed onto the platform 132 as needed.The material feeder 102 can have adjustable features to hold differentsize sheets. The platform 132 is raised or lowered using one or morelead screws 134 driven by one or more motors 136. While the embodimentin FIGS. 11 and 12 shows four lead screws 134 and a single stepper motor136 with a belt for driving the lead screws 134, the platform 132 couldbe driven by a single lead screw and stepper motor, or any othercombination of lead screws and stepper motors, or by a belt-drivensystem, or by any other suitable mechanisms known in the art orhereafter invented. The motors 136 are turned on and off by signals froma controller.

A distance sensor 138 is mounted on or in relation to the frame 130. Thedistance sensor 138 detects, as the platform 132 moves upward, when thetop of the stack of substrate sheets 202 reaches a pre-defined distancefrom the sensor, known as the “sheet feed position.” The distance sensor138 can be any type of suitable sensor, including an optical distancesensor, such as, but not limited to, an encoder, a time of flightdistance sensor or IR sensor. The distance sensor 138 is incommunication with the controller. As the platform 132 moves upward,when the distance sensor 138 detects that the top of the stack ofsubstrate sheets 202 has reached the pre-defined distance from thesensor 138 (the sheet feed position), the sensor 138 sends a signal tothe controller indicating this condition. Upon receiving the signal fromthe distance sensor 138, the controller causes the motors to stop sothat the platform 132 comes to a rest. Alternatively, a different kindof sensor can be used based on a switch which has a probe which moves upand down as the plate is pressed on the sheets.

Sheet Openings. In one embodiment, each substrate sheet includes atleast two notches 204 or areas and at or near its edges, where materialis removed or otherwise not present, as shown in FIG. 2. These notches204 can be created for example by laser cutting, die cutting, or anothermethod. In a first orientation, the notches 204 are at or near the topof the right-hand side of the sheet 202 and the bottom of the left-handside of the sheet 202. In a second orientation, the notches 204 are ator near the top of the left-hand side of the sheet and the bottom of theright-hand side of the sheet. The sheets 202 are stacked in alternatingfashion, so that a sheet of the first orientation is always between twosheets of the second orientation and vice versa, as shown in FIG. 2.Notches may serve usefully for orderly feeding of sequential sheets,registration among multiple processed sheets, or both. In preferredembodiments, printer-punched holes are used for such registration.

Hold-Down Prongs and Gripper. Two pairs of hold-down prongs 142 aremounted on the frame 130 for the material feeder 102. Each hold-downprong 142 is operably connected to a shaft 144 of a stepper motor 146for pressing the prong 142 about the shaft 144. The stepper motors 146are in communication with the controller. Each hold-down prong 142comprises an optional foot 148 that includes a sheet-engaging surface.One pair of hold-down prongs 142 is positioned so that the feet 148thereof align with the openings in substrate sheets of the firstorientation and the other pair of hold-down prongs 142 is positioned sothat the feet 148 thereof align with the openings in substrate sheets ofthe second orientation.

Detailed Operation. When the platform 132 reaches the sheet feedposition (and assuming it is time to advance the next sheet from thefeeder 102 to the printer 104), the controller sends a signal to thestepper motor of the XYZ positioner 116 that controls the Z movement ofthe Coanda gripper 118 to lower the gripper towards the top of the stackof substrate sheets 202. As the Coanda gripper 118 nears the top of thestack of substrate sheets 202, the controller sends a signal to turn onthe forced air to the Coanda gripper 118 thereby activating it. Thecontroller also sends a signal to stepper motors 146 causing theirshafts 144 to rotate so that the hold-down prongs 142 connected to theshaft 144 which are pressed into the stack of sheets 202 and the feet148 and thereof pass through the notches 204 in the top substrate sheet202 and engage the surface of the substrate sheet below the top sheet(hereinafter “second sheet”). This could occur before, during, or afterthe movement of the Coanda gripper 118. The sheet-engaging surfaces ofthe feet 148 can optionally include a textured surface to ensure abetter grip with the substrate sheet 202. The textured surface can beintegral to the foot 148 or, for example, can be an additional materialadhered, fastened or applied to the sheet-engaging surface of the foot148, such as, but not limited to, sandpaper.

Each foot 148 can further include a connector 156 for attaching a forcedair hose 122, conduits for channeling forced air through the foot 148,and vents 158 for forced air to pass out of the foot 148. The oppositeends of the forced air hoses 122 are connected to a manifold (not shown)comprising air valves so that the forced air to each hose 122 can beturned on or off The manifold is in communication with the controller.

When the Coanda gripper 118 comes near the top sheet of the stack ofsubstrate sheets 202, the stepper motor 146 sends a signal to thecontroller and then the controller sends a signal to the manifoldinstructing it to open the valves supplying air to the feet 148. Thiscauses forced air to pass through the vents 158 and thus between the topsubstrate sheet and the sheet engaged by the feet 148, i.e., a secondsheet. The Coanda forces from the gripper then lift the top substratesheet. The vents 158 are designed so that the air blows in spreadfashion across a desired angle, for example to both the left and rightof center, and slightly downward from the horizontal plane. The spreadangle can vary based on a number of factors, such as the pressure of theforced air, the weight and porosity of the substrate sheets, the size ofthe sheets, and the location of the openings in the sheets. In general,this spread angle may be chosen so that the air flow maximizesseparation between the top sheet and the second sheet. The combinationof the feet 148 engaging the surface of the second sheet and the forcedair between the top sheet and second sheet enables the Coanda gripper118 to be able to lift and move the top sheet without also lifting thesecond sheet (or any sheets below the second sheet), and also withoutthe second sheet sticking to the top sheet due to frayed fiberentanglement or otherwise.

After the first sheet is transferred to the printer 104, as furtherdescribed below, the second sheet then becomes the top sheet of thestack to be transferred, and the process described above is repeated,but the other pair of hold-down prongs 142 are used, since they alignwith the openings in the second sheet and thus will pass through thoseopenings to engage the surface of the sheet below the second sheet(which is now the top sheet).

In the embodiment described above, in addition to supplying forced airthrough the feet 148 of the hold-down prongs 142, air nozzles 150 orother blowers can be mounted on, or in relationship to, the frame 130and used to blow air above or across the top surface of the topsubstrate sheet, creating Bernoulli forces to help lift the sheet. Suchadditional nozzles or blowers 150 can also be used to provide additionalair between the top sheet and the one below it. In a further alternativeembodiment, forced air is not supplied through the feet 148 of thehold-down prongs 142 and is provided through the above-describedindependent nozzles or blowers 150 mounted on or in relationship to theframe 130. Any of the many alternative ways of providing forced aircould also be used, for example, but not limited to, through areas ofthe prongs 142 other than the feet 148 or through nozzles mounted on theprongs 142.

Slip Sheet Embodiment.

In an alternative embodiment of the material feeder 102, hold-downprongs 142 are eliminated and forced air need not be directed betweenthe sheets. Additionally, the sheets 202 need not include notches 204.Instead, a non-porous slip sheet, such as paper, is added between eachpair of substrate sheets in the stack of sheets 202. A suitable gripper,such as a vacuum gripper or needle gripper, is then able to pick up thetop substrate sheet without picking up any other substrate sheets. Inthis embodiment, depending on the gripper used, after the top substratesheet is transferred to the printer 104, the slip sheet will reside atthe top of the stack of sheets 202 and can then be picked up anddiscarded using a suitable gripper or any other means. If the gripperused to pick up the substrate sheet is such that it also picks up theslip sheet, then the slip sheet can be removed at a later step in theprocess. This approach using slip sheets can be generally lesspreferable, because it requires an additional area to place the slipsheets after they are lifted from the stack, requires morepre-processing to create the stack of sheets (i.e., with a slip sheetinterleaved between each pair of substrate sheets), and produces a largenumber of slip sheets which have to be either discarded or recycled, butit is contemplated that it might be useful in certainapplications/embodiments.

Transfer of Sheets to the Printer.

After the gripper 118 grips the top sheet in any of the mannersdescribed above, the controller sends a signal to the stepper motorcausing the gripper 118 to move upward a pre-defined distance. Thedistance sensor 138 can be used to confirm that the gripper 118 isholding a sheet. Once confirmed, or when the gripper 118 otherwisebegins to move away from the stack of sheets 202, the controller sends asignal to the manifold turning off the air to the hold-down prongs 142and then sends a signal to the stepper motor 146 to rotate the hold-downprongs 142 off of the second sheet. Meanwhile, the controller also sendsa signal to the XY positioner, causing the gripper 118 to move towardsthe printer platen 140. When the gripper 118 reaches a pre-definedposition over the platen 140, the controller sends signals to thestepper motor 146 and air manifold so that the substrate sheet islowered and placed on the platen 140 and the gripper 118 releases thesheet so that the substrate sheet is resting on the platen 140. Thegripper 118 and XYZ positioner 116 are designed so that they locate thesheet on the printer platen 140 with good precision. The controller thensends a signal to the XYZ positioner 116 causing the gripper 118 toreturn to its initial position above the material feeder 102.

Although the present description uses an XYZ positioner, it will beclear to one of skill in the art that the system can be built withsimply an XZ positioner moving the grippers left and right and up anddown or even an X positioner moving the grippers left and right but withthe positioners located in such a manner as not to require up and downmovement.

Printer.

The printer 104 is activated using a controller typical under programcontrol of a computer to print the layer shapes onto the substrate sheetin the manner previously described. In this operation, the positioner onwhich the print heads 105 are mounted can be stationary, such that theprint heads 105 move only in the Y-direction and the sheet is advancedunder the print heads 105 by movement of the platen 140 in theX-direction. Alternatively, the platen 140 can be held stationary duringthe printing operation and the positioner on which the print heads 105are mounted can be advanced along the length of the substrate sheet asthe print heads 105 are moved in either the X- or Y-direction. In eithercase, it is preferred that the printer 104 operates such that when theprinting of layer shapes onto the substrate sheet is completed, theplaten 140 is positioned so that the substrate is situated between thelocation of the positioner hosting the print heads 105 and the locationof the powder applicator 108.

Punches.

The printer 104 may also optionally include one or more punches, eithermounted on the same positioner arm as the print heads 105 or separatelymounted in relation to the printer platen 140, so that, during orimmediately prior to or after the printing operation, holes can bepunched in the substrate sheet in desired locations. The holes are usedlater in the process to align the substrate sheets by loading them ontoregistration or alignment pins. Those pins can be part of a stackersubsystem, or part of a subsequent stacking operation, or both. Ineither case, preferably, the diameter of the holes is similar to theouter diameter of the registration pins to get the best registration.The punch can be, for example, a hole punch, a paper drill, or any othersuitable mechanism known in the art. The punch can optionally include amechanism for vacuuming the chads that are punched from the substratesheets, or a separate vacuum, sweeping, or blowing mechanism canoptionally be provided.

The locations for the holes on the substrate sheet are defined inrelationship to where the layer shapes for the 3D part will be printedon the substrate sheet. The information about the hole locations isprovided to the printer 104 along with the layer shape information. Thecomputer for the printer 104 can generate signals to cause holes to bepunched at the desired locations.

If the system does not include a punch or other mechanism for formingholes in the substrate sheets, then holes can optionally be created inthe sheets as a precursor or post processing step. Alternatively thecorners of the sheet can be used for regstration. The layer can also bedie cut using a die cutting station that is well known in the art andthis can be done before or after printing and should in register withthe printing. There are also a number of other ways of making holes thatare well known in the art such as laser cutting.

Transfer of Sheets to Powder Applicator.

Upon completion of printing and, if included, punching, the needlegripper 120 is used to transfer the substrate sheet 202 a . . . n to thepowder system 106, which includes a conveyor 152 for feeding thesubstrate sheet into the powder applicator 108. More specifically, theprinter 104 sends a signal to the controller, which then sends signalsto the XYZ positioner 116, stepper motor 146, and air manifold so thatthe XY positioner moves the needle gripper 120 to a position above thesubstrate sheet (resting on the printer platen 140), the stepper motormoves the gripper downward until the needle gripper 120 contacts the topof the substrate sheet, and the manifold opens the air valve attached tothe needle gripper 120 to activate it and thereby grip the substratesheet. A preferred implementation uses a pneumatic cylinder forZ-movement, and only an X-positioner is used. As previously mentioned, aroll/web based system for feed can be used. The controller then sendsfurther signals so that the stepper motor lifts the gripper (and thusthe substrate sheet) upward, the XY positioner moves the gripper to anappropriate position above the conveyor 152 of the powder applicator108, the stepper motor moves the gripper downward until the substratesheet is placed on the surface of the conveyor 152, and then the gripperreleases the substrate sheet onto the conveyor 152. The needle gripper120 and XYZ positioner 116 are designed so that they locate the sheet onthe conveyor 152 with good precision. The XY positioner then moves thegripper upwards and back to its original position to await the nextsheet to be run through the printer 104.

If there is an error with the sheet, detected for example by a camera,the printer 104 can send an indicating signal to the controller and thecontroller can send a signal to the XYZ positioner 116 for the needlegripper 120 50 that, instead of transferring the substrate sheet to thepowder applicator 108, the sheet is transferred to a discard area.

A needle gripper 120 suffices to pick up a substrate sheet 202 a . . . nresting on the printer platen 140. This is facilitated by the fact thata single sheet is resting on the surface of the platen 140 rather thanon a stack of substrate sheets 202. A felted gripper configured so thatthe felted material and pins do not interfere with or materially disturbthe printing fluid that the printer 104 deposits onto the substratesheet, could alternatively be used. Likewise, other gripper embodimentsdescribed herein or known in the art could be used. In general, a Coandagripper is not as suitable for use in this configuration to transfersheets from the printer platen 140 to the powder applicator 108. This isbecause there is no airflow under the sheet on the platen 140, which isa requirement for a Coanda gripper. This problem can be solved byintroducing air below the sheet resting on the printer.

Though Coanda grippers and needle grippers are described in the detailedembodiments herein, the invention is not intended to be limited to such.Any gripper now existing or hereinafter invented that is capable ofgripping or lifting substrate sheets, and particularly non-woven orotherwise porous substrate sheets, under the conditions herein describedwould be suitable for use in the invention.

Powder System.

As shown in FIG. 1, the powder applicator 108 and powder remover 110 areintegrated to form a single component, the powder system 106. They mayalternatively be provided as separate components. In either case, thepowder system 106 can be set to run continuously so that, once asubstrate sheet 202 a . . . n is placed upon the conveyor 152, itautomatically travels through the powder system 106. Alternatively, acontroller in communication with both the XYZ positioner 116 and thepowder system 106 can instruct the powder applicator 108 and powderremover 110 or subsystems thereof to turn on and off at the appropriatetimes.

The powder applicator 108 deposits powder, such as, but not limited to,thermoplastic powder, onto the surface of the substrate sheet (on whichlayer shapes have just been printed). The powder sticks to the printed(wet) areas on the sheet. The powder remover 110 then removes any powderthat did not adhere to the sheet.

As an example, the powder can be applied by a device that is used inthermography machines such as those made by THERM-O-TYPE Corp, in whichthe powder applicator 108 and powder remover 110 are integrated into asingle component. Such a device is shown in FIG. 1 and FIGS. 13-17 andconsists of(i) a series of conveyors, (ii) a vibrating trough that holdstypically polymer powder and has a slit through which powder flows todeposit powder on the sheet while it moves under the trough, and (iii) avacuum 110 that removes the powder that did not adhere to the sheetwhile it moves under the vacuum 110. The vacuum subsystem which includesa vacuum motor and cyclone 154 sits above the conveyor 152. In the areabelow the vacuum subsystem, a series of star wheels are configured tohold the sheet down while it is exposed to the airflow of the vacuumsubsystem. The cyclone 154 also re-circulates the vacuumed powder backto the trough for reuse. By use of the powder system 106, in addition toremoving powder that does not adhere to the sheet, powder remains on theprinted areas as previously described.

The cyclone 154 that is used in the THERM-O-TYPE and other similarmachines removes, through its exhaust, a high percentage of particlesand has a cutoff point of about 50 microns, that is, it does not recyclemost particles that are smaller than 50 microns. It has been discoveredthat, when this happens, it substantially reduces the amount of powderdeposited on the sheet and further means that a significant amount ofpowder is wasted, since the purpose of the cyclone 154 is to permitrecycling of the powder. Part of the reason that the amount of powderdeposited is decreased is that smaller particles are no longerdeposited, which in turn reduces the total amount of powder depositedand, over time, most of the smaller particles are removed through therecycling process. When there are smaller particles in the distribution,the amount of powder deposited increases. Having a powder with adistribution of powder sizes centered at 50 microns works well, so thecutoff point of 50 microns removes a large percentage of particles,about 30%.

This problem is resolved by an alternative powder system embodiment 180,shown in FIGS. 18-23, or a dump valve assembly 180. The dump valveassembly 180 consists of a dump valve body 181, a dump valve 182, awasher bearing 183, a dump valve shaft 184, a retaining ring 185 (ofsize, e.g., 5/16″), a gear motor 186 (e.g., 1/120 hp), a flexiblecoupling 187, and a dump valve motor bracket 188. In this embodiment,the cyclone design is replaced with a conical design, such as, forexample, the design used in the Dust Deputy. This design has a cutoffpoint that is much lower, on the order of a few microns, and thereforerecycles over 95% of the powder. This leads to a high powder loaddeposition, since it does not lose smaller particles, and there is muchless waste of particles. Additionally, the cyclone-based implementationhas a “valve” 195 on the powder removal system that collects the powderin a tube 189 with oval holes 190 that revolves inside a housing (FIG.22) and that alternately collects and then dumps the powder into thetrough of the Thermograph. In the alternative embodiment, in addition tomodification/replacement of the cyclone with a conical design, this tubeis replaced with a delrin tube 189 (FIG. 23) having multiple slots 191instead of the oval opening 190. This produces a better seal and stopsair from coming in from below, preventing the powder from falling intothe tube 189.

Additional Powder Removal.

In certain circumstances the amount of powder removal from the vacuum110 is insufficient since some unwanted powder may still reside withinthe substrate sheet material. For this reason an air knife 160, such as,but not limited to, the X-Stream Air Blade Air Knife from Nex Flow AirProducts Corp., can be added after the vacuum stage so that anyremaining excess powder on the substrate sheet is removed (FIG. 1). Theair knife 160 can be controlled by a programmed microcontroller.

In addition, the powder system 106 can be configured so that sheets gothrough the powder applicator and powder removal stages more than onetime. The advantage is that depositing powder onto a substrate sheet inmultiple trips can increase the amount of powder that adheres to theprinted areas of the substrate sheet, which sometimes is desirable formaking the 3D part. After the sheet completes transit through the powdersystem, the conveyors 152 may be reversed so that the sheet travels backto the entrance of the powder applicator 108 and then reversed again(now going forward) so that the sheet goes back through the powdersystem 106 again. In this embodiment, during travel in the reversedirection, one or both of the powder applicator 108 and powder vacuum110 could be turned off. In an alternative embodiment, after a sheetexits the powder remover 110, a separate conveyor or transfer system cancarry the sheet back to the conveyor associated with the entrance to thepowder applicator 108, whereupon the sheet will travel back through thepowder system 106. In these embodiments, the sheet may be flipped usingany suitable mechanism known in the art, so that powder is applied theother side of the sheet. These steps can be repeated as many times asdesired.

Fuser.

After the sheet has had powder applied and excess powder has beenremoved, it can be advantageous to melt the remaining powder on thesheet (i.e., the powder adhered to the printed areas of the sheet) sothat the powder more permanently affixes to the sheet and is thusprotected from displacement, disruption, or falling off duringsubsequent processing steps. To this end, an optional fuser component112 (FIG. 1) may be disposed after the powder system 106. The fuser 112may be disposed above, below, or adjacent to the conveyor 152 leadingout of the powder remover 110. The fuser 112 may be, for example but notlimited to, radiant, IR, or other heating method sufficient to melt andthus fix the powder to the sheet. As the sheet travels out of the powderapplicator 108, the heat from the fuser 112 melts the powder on thesubstrate sheet causing it to fix to the sheet.

Further embodiments.

Fiber Orientation.

If one is using substrates in which the fibers are arranged in aparticular direction, such as unidirectional material or wovenmaterials, the transfer system can be adapted so that the gripper isrotatable. This way, the sheets picked up by the gripper can be rotated,for example by 30, 45, or 90 degrees, before they are placed on theprinter platen 140, so that when the sheets are finally stacked to makethe 3D part, they have varying angles of fiber orientation relative toone another. This enables production of objects with better mechanicalproperties in multiple directions. Alternatively, instead of rotatingthe sheets prior to printing, the sheets may be rotated at any one ofseveral other points along the process. The sheets may, for example, berotated just after printing, using a turntable, by rotating the needlegripper 120, or by other rotating means. The sheets may also be rotatedafter powder removal or after fusing, in either case also using aturntable, by introducing another gripper at those locations that iscapable of rotating the sheets, or by other rotating means known in theart. Another way to adjust directionality of the fibers is to usemultiple sheet trays, with each sheet tray holding sheets in a differentdirection.

With an understanding of where along the process and to what degree thesheets will be rotated, the printer 104 prints the layers shapes of the3D part in a corollary rotation so that, when the substrate sheets arestacked, the layer shapes from one substrate sheet to another areproperly oriented for making the 3D part. Substrate sheet shapes otherthan squares or rectangles may also be used so that, when sheets arerotated and then stacked, all of the edges of the sheets in the stackwill be aligned. For example, such other sheet shapes could include, butare not limited to, circles, octagons, and any other symmetric regularpolygons. Additionally, sheets may be cut on different biases so thatthe fiber orientation can be varied, such as, for example, by 45 and 90degrees, and then stacked in the appropriate order (at the sheet feedingstep), thus eliminating the need to rotate the sheets.

Roll or Web Feeding.

Instead of using substrate sheets, a roll of substrate material may beused in the CBAM process and system described herein. FIG. 24 depicts acontinuous feed roll implementation 400, and FIG. 25 depicts a roll tosheet implementation 500. In these embodiments, a roll of substratematerial 402 is mounted and situated ahead of the printer 104. Atensioning system 404 together with feed rollers 406 are used to holdand advance the web defined by the length of the roll material fedthrough the system. The web 402 can extend through all of the componentsof the system—printer 104, powder applicator 108, powder remover 110,and, if present, fuser 112—and then be cut by a cutter 408 into singlesheets prior to stacking. This is depicted in FIG. 24. Alternatively, asdepicted in FIG. 25 the web 402 may be cut by the cutter 408 into singlesheets at any prior point in the process. For example, the web 402 maybe converted to a single sheet prior to advancing the resulting sheetonto the printer platen 140. The web 402 may be converted to a singlesheet after the leading edge is situated on the platen 140. The web 402may be converted to a single sheet after the printing operation iscompleted and before the resulting sheet is fed into the powderapplicator 108, and so on.

Additional Sensors.

This apparatus can also optionally have a camera with vision software toensure that it has not malfunctioned, that the appropriate amount ofpowder is deposited, that the sheets are moving as desired, and otherquality assurance aspects of the process. Additional sensors mayoptionally be attached to the sheet feeder 102 to make sure that a sheethas been picked up, or that not more than one sheet has been picked up,or that no other malfunction has occurred. If the machine has not pickedup a sheet, the operation can be run again. If two sheets are picked up,then rather than being transferred to the printer platen 140, they canbe placed into a separate pile for reuse later or discarding. Themachine may optionally have a light, buzzer, other alert, or anycombination thereof, to inform the operator of the malfunction, at whichpoint the problem can be addressed.

Controllers.

The process carried out by the system may be sequenced and monitoredusing microcontrollers or PLCs as follows. The sheet feeder 102 isinformed by the control program to feed a sheet. After feeding a sheetonto the printer platen 140, the feeder 102 informs the control programwhich tells the printer 104 to begin printing. When the printer 104 hascompleted printing, it informs the positioner to move the needle gripper120, which picks up the sheet 202 a . . . n and deposits it on thepowdering conveyor 152 and then informs the control program it hascompleted its task. These steps can optionally be overlapped, i.e., runin parallel as described above, in order to increase the speed of theprocess.

Printheads.

In embodiments described above, the printheads 105 are designed forrastering movement to deposit printing fluid on the substrate sheets202. Alternatively, by using multiple inkjet heads staged across thewidth of the substrate sheet (or roll/web), or by using page-width headslike the Memjet head, the need for rastering can be eliminated. Thisenables the system to print much faster. For example, with certainheads, the system can be made to run at rates of up to 60 pages perminute or much higher, thus producing parts at speeds that rivalinjection molding speeds. Additionally, the print heads 105 mayoptionally be equipped with a bulk ink delivery system, so that thefluid used will need to be replaced less frequently.

It will further be clear to one of skill in the art that any of theelements of this design can be replaced with other elements with similarfunctions. This design can also be configured to be field-upgradable, sothat individual elements can be replaced, improving the performance ofthe machine.

While preferred embodiments are disclosed, many other implementationswill occur to one of ordinary skill in the art and are all within thescope of the invention. Each of the various embodiments described abovemay be combined with other described embodiments in order to providemultiple features. Furthermore, while the foregoing describes a numberof separate embodiments of the apparatus and method of the presentinvention, what has been described herein is merely illustrative of theapplication of the principles of the present invention. Otherarrangements, methods, modifications, and substitutions by one ofordinary skill in the art are therefore also considered to be within thescope of the present invention, which is not to be limited except by theclaims that follow.

The invention claimed is:
 1. An apparatus for the automated preparationof a plurality of substrate sheets that correspond to cross sections ofa three-dimensional (3D) object manufactured by additive manufacturingof composite-based objects, comprising: a material feeder capable ofholding the plurality of substrate sheets; a printer configured todeposit fluid onto a particular substrate sheet from the plurality ofsubstrate sheets; a powder system having a powder applicator and apowder remover; the powder applicator constructed to deposit powder ontothe particular substrate sheet; the powder remover constructed to removepowder that did not adhere to the particular substrate sheet; and, atransfer system for transferring the particular substrate sheet from thematerial feeder to the printer, and from the printer to the powdersystem.
 2. The apparatus of claim 1, wherein the transfer systemcomprises: a first gripper for transferring at least one substrate sheetfrom the plurality of substrate sheets from the material feeder to theprinter; a second gripper for transferring at least one substrate sheetfrom the plurality of substrate sheets from the printer to the powdersystem; and one or more positioners for positioning one or more of thegrippers.
 3. The apparatus of claim 2, wherein the first and secondgrippers are activated with forced air through a pair of air hoses eachconnected at a first end to its gripper, of the first and secondgrippers, and at a second end to a manifold with air valves for startingand stopping the flow of air to the grippers.
 4. The apparatus of claim3, wherein first stepper motors, or first solenoids or first pneumaticpositioners move the first and second grippers in an XY-direction, andsecond stepper motors, or second solenoids, or second pneumaticpositions move the first and second grippers in a Z-direction.
 5. Theapparatus of claim 4, further comprising a controller providing signalsto open and close the air valves or to turn the first and second steppermotors or first and second solenoids or first and second pneumaticpositioners on and off.
 6. The apparatus of claim 1, wherein thetransfer system comprises: a felted-material gripper for transferring atleast one substrate sheet from the plurality of substrate sheets fromthe material feeder to the printer; a needle gripper for transferring atleast one substrate sheet from the plurality of substrate sheets fromthe printer to the powder system; and one or more positioners forpositioning the felted-material gripper and the needle gripper.
 7. Theapparatus of claim 1, wherein the transfer system comprises: a first andsecond gripper providing adhesive or electrostatic forces fortransferring a sheet from the material feeder to the printer.
 8. Theapparatus of claim 1, wherein the printer comprises print heads, andalso includes one or hole makers, mounted either upstream or downstreamof the print heads, configured to create holes to align at least one ofsubstrate sheet of the plurality of substrate sheets for loading ontoregistration pins.
 9. The apparatus of claim 8 wherein the hole maker ismechanical.
 10. The apparatus of claim 9 wherein the hole maker is apunch.
 11. The apparatus of claim 8 wherein the hole maker is a lasercutter.
 12. The apparatus of claim 1 wherein the plurality of substratesheets are supplied as a plurality of discrete sheets.
 13. The apparatusof claim 1 wherein the plurality of substrate sheets are supplied as aweb.
 14. The apparatus of claim 12 wherein the transfer system isconfigured to pull the web through the apparatus.
 15. The apparatus ofclaim 13 further comprising a cutter constructed to cut the web intodiscrete substrate sheets.
 16. An apparatus for the automatedpreparation of substrate layers that correspond to cross sections of athree-dimensional (3D) object manufactured by additive manufacturing ofcomposite-based objects, comprising: a material feeder that holds a rollof substrate material, wherein material from the roll of substratematerial is threaded through a printer and a powder system; a tensioningsystem cooperating with the material feeder to hold and advance thesubstrate material from the roll to the printer, and from the printer tothe powder system; wherein, the substrate material moves from the rollthrough the apparatus as the roll unwinds; the printer being configuredto deposit fluid on subsequent sections of the material from the roll asthe material from the roll passes through the printer; the powder systemhaving a powder applicator and a powder remover, wherein the powderapplicator deposits powder onto subsequent sections of the substratematerial from the roll as the substrate material from the roll passesthrough the powder system such that the powder adheres to areas ontowhich the printer has deposited fluid, and the powder remover removesany powder that did not adhere.
 17. The apparatus of claim 16 includinga cutter constructed to separate substrate sheets from the roll ofsubstrate material.
 18. The apparatus of claim 17 wherein the printerincludes one or more hole maker mounted either upstream or downstream ofthe print heads, configured to create holes in the substrate sheets toalign the substrate sheets for loading onto registration pins.
 19. Theapparatus of claim 18 wherein the one or more hole maker is a punch. 20.The apparatus of claim 18 wherein the one or more hole maker is a lasercutter.